Degradable particulate generation and associated methods

ABSTRACT

Herein provided are methods for producing degradable particulates at a drill site, and methods related to the use of such degradable particulates in subterranean applications. In one embodiment, the present invention provides a method comprising: providing a degradable polymer solvent mixture that comprises a degradable polymer and a first solvent; and mixing the degradable polymer solvent mixture with a second solvent at a drill site with shear to form a solid liquid dispersion comprising a solid phase and a liquid phase, the solid phase comprising degradable particulates and the liquid phase comprising the first solvent and the second solvent.

BACKGROUND

The present invention relates generally to facilitating the use ofdegradable particulates. More particularly, the present inventionrelates to methods for producing degradable particulates at a drillsite, and methods related to the use of such degradable particulates insubterranean applications.

Degradable particulates comprise degradable materials (which areoftentimes degradable polymers) that are capable of undergoing anirreversible degradation when used in subterranean applications, e.g.,in a well bore. As used herein, the terms “particulate” or“particulates” refer to a particle or particles that may have a physicalshape of platelets, shavings, fibers, flakes, ribbons, rods, strips,spheroids, toroids, pellets, tablets, or any other suitable shape. Theterm “irreversible” as used herein means that the degradable materialshould degrade in situ (e.g., within a well bore) but should notrecrystallize or reconsolidate in situ after degradation (e.g., in awell bore). The terms “degradation” or “degradable” refer to both thetwo relatively extreme cases of hydrolytic degradation that thedegradable material may undergo, e.g., heterogeneous (or bulk erosion)and homogeneous (or surface erosion), and any stage of degradation inbetween these two. This degradation can be a result of, inter alia, achemical or thermal reaction, or a reaction induced by radiation. Theterms “polymer” or “polymers” as used herein do not imply any particulardegree of polymerization; for instance, oligomers are encompassed withinthis definition.

The degradability of a degradable polymer often depends, at least inpart, on its backbone structure. For instance, the presence ofhydrolyzable and/or oxidizable linkages in the backbone often yields amaterial that will degrade as described herein. The rates at which suchpolymers degrade are dependent on the type of repetitive unit,composition, sequence, length, molecular geometry, molecular weight,morphology (e.g., crystallinity, size of spherulites, and orientation),hydrophilicity, hydrophobicity, surface area, and additives. Also, theenvironment to which the polymer is subjected may affect how itdegrades, e.g., temperature, presence of moisture, oxygen,microorganisms, enzymes, pH, and the like.

The physical properties of degradable polymers depend on several factorssuch as the composition of the repeat units, flexibility of the chain,presence of polar groups, molecular mass, degree of branching,crystallinity, orientation, etc. For example, short chain branchesreduce the degree of crystallinity of polymers while long chain brancheslower the melt viscosity and impart, inter alia, extensional viscositywith tension-stiffening behavior. The properties of the materialutilized can be further tailored by blending, and copolymerizing it withanother polymer, or by changing the macromolecular architecture (e.g.,hyper-branched polymers, star-shaped, or dendrimers, etc.). Theproperties of any such suitable degradable polymers (e.g.,hydrophobicity, hydrophilicity, rate of degradation, etc.) can betailored by introducing select functional groups along the polymerchains. For example, poly(phenyllactide) will degrade at about one fifthof the rate of racemic poly(lactide) at a pH of 7.4 at 55° C.

To obtain degradable particulates that may be used in subterraneanapplications (e.g., as acid precursors, fluid loss control particles,diverting agents, filter cake components, drilling fluid additives,cement additives, etc.), off-site processes may be used wherein thedegradable particulates are manufactured and then those particulates aretransported to a drill site for use. Common manufacturing processesinclude cryogenic grinding, which is an expensive process that involvesgrinding a degradable polymer, such as poly(lactic acid), at cryogenictemperatures to form particulates having a desired shape and size.Oftentimes, these grinding processes are inefficient, requiring multiplepasses through equipment, usually resulting in corresponding yieldlosses. Also, mechanical classification (e.g., mechanical classificationto separate different size particulates to obtain a specific sizedistribution) often is required to obtain narrow particle sizedistributions, which generally are desired. Another method that may beused to make degradable particulates off-site is spray drying. Spraydrying processes usually involve dissolution of a degradable polymersample in a volatile solvent (which can be an environmental problemitself), and spraying the solution into a stream of hot gas to makedegradable particulates. Such processes generally need to be carried outin a specially designed factory setting, and the large scale productionof degradable particulates may not be practicable. Another method ofproducing degradable particulates is an extrusion method; however,extrusion methods generally are not useful for making degradableparticulates that are less than about 500 microns in size.

One problem with making degradable particulates off-site to be used insubterranean applications that are located at drill sites is that theability to respond to changes in conditions that are encountered in aparticular application is hampered because there is no flexibility tochange the composition or properties of the particulates once they areat the drill site. This may be problematic, for instance, if theconditions of a particular application dictate that certain degradableparticulates should be used to obtain a given result. One example iswhere it may be desirable to change the particle size distribution ofthe degradable particulates for a fluid loss control operation. If theparticulates are not made at the drill site, then the operator has alimited ability to alter that characteristic of the degradableparticulates. Thus, operators are unable to respond to conditionsencountered during subterranean conditions in terms of providing themost desirable degradable particulates for that application.

Moreover, transportation of degradable particulates made in an off-siteprocess to a drill site may be especially problematic. The conditionsencountered while shipping may pose hazards to the degradableparticulates that may negatively impact their properties orcharacteristics.

SUMMARY

The present invention relates generally to facilitating the use ofdegradable particulates. More particularly, the present inventionrelates to methods for producing degradable particulates at a drillsite, and methods related to the use of such degradable particulates insubterranean applications.

In one embodiment, the present invention provides a method comprising:providing a degradable polymer solvent mixture that comprises adegradable polymer and a first solvent; and mixing the degradablepolymer solvent mixture with a second solvent at a drill site with shearto form a solid liquid dispersion comprising a solid phase and a liquidphase, the solid phase comprising degradable particulates and the liquidphase comprising the first solvent and the second solvent.

In another embodiment, the present invention provides a methodcomprising: providing a treatment fluid, the treatment fluid comprisingdegradable particulates, the degradable particulates having been made bya precipation method at a drill site; and introducing the treatmentfluid into a well bore penetrating a subterranean formation at the drillsite.

In another embodiment, the present invention provides a methodcomprising: providing a degradable polymer solvent mixture thatcomprises a degradable polymer and a first solvent; mixing thedegradable polymer solvent mixture with a second solvent at a drill sitewith shear to form a solid liquid dispersion comprising a solid phaseand a liquid phase, the solid phase comprising degradable particulatesand the liquid phase comprising the first solvent and the secondsolvent; and introducing the second solvent and at least a portion ofthe degradable particulates into a well bore penetrating a subterraneanformation at the drill site.

The features and advantages of the present invention will be readilyapparent to those skilled in the art upon a reading of the descriptionof the embodiments that follows.

DESCRIPTION

The present invention relates generally to facilitating the use ofdegradable particulates. More particularly, the present inventionrelates to methods for producing degradable particulates at a drillsite, and methods related to the use of such degradable particulates insubterranean applications.

The present invention provides methods of generating degradableparticulates at a drill site. The term drill site, as used herein,refers to the workplace at the site of a drill hole (sometimes referredto as a well bore or borehole) before, during, and after production. Thedegradable particulates can be made at the drill site for use in a wellbore located at the drill site. In certain embodiments, the degradableparticulates may be made and then stored at the drill site until adesired time for use. In other embodiments of this invention, thedegradable particulates can be made at the drill site and then usedrelatively quickly in a chosen subterranean application. The storabilityof the degradable particulates made, and the particular application inwhich they will be used, likely will dictate whether storage orimmediate use is preferred. One of the many advantages offered by themethods and compositions of the present invention is the ability tomodify the degradable particulates to respond to changes in conditionsand requirements. For instance, the particle size distribution orrelative pliability could be modified based on the particularsubterranean conditions encountered. Another advantage is thattransportation costs and conditions that may harm the degradableparticulates may be avoided and/or reduced. Examples of subterraneanapplications in which the generated degradable particulates could beused include, but are not limited to, such applications as fluid losscontrol particles, as diverting agents, as filter cake components, asdrilling fluid additives, as cement composition additives, or otheracid-precursor components.

The degradable particulates made in conjunction with a method of thepresent invention can be placed into a subterranean formation with orwithout a treatment fluid, or they may be stored in a suitablecollection container located at or near the drill site for use at adesired time, depending on the storability of the particulates. As usedherein, the term “treatment fluid” refers to any fluid that may be usedin a subterranean application in conjunction with a desired functionand/or for a desired purpose. The term “treatment fluid” does not implyany particular action by the fluid or any component thereof. In someembodiments, a particular treatment fluid with which the degradableparticulates will be placed into a well bore may be incorporated into amethod of making the degradable particulates, e.g., as a solvent orfluid in the process. The degradable particulates may have differingproperties, such as, relative hardness, pliability, degradation rate,etc. depending on the processing factors, the type of degradable polymerused, etc. The specific properties of the degradable particulatesproduced may vary by varying certain process parameters (includingcompositions), which will be evident to one of ordinary skill in the artwith the benefit of this disclosure.

The methods of this invention include emulsion methods, precipitationmethods, melt coagulation methods, and supercritical fluid assistedmethods.

The Emulsion Methods of This Invention

The present invention provides emulsion methods that may be used togenerate degradable particulates of a suitable or desirable size andshape at a drill site for use in subterranean applications. Thedegradable particulates can be used in a subterranean application withor without a treatment fluid, depending on the use.

Generally, certain embodiments of the emulsion methods of this inventioncomprise providing a degradable polymer solvent mixture that comprises adegradable polymer and a first solvent; adding the degradable polymermixture to a second solvent with sufficient shear to form an emulsionthat comprises a discontinuous phase and a continuous phase, thediscontinuous phase comprising the degradable polymer mixture and thecontinuous phase comprising the second solvent; removing a sufficientamount of the first solvent from the discontinuous phase so thatdegradable particulates begin to form; and allowing a dispersion ofdegradable particulates to form in the continuous phase. The firstsolvent can be removed from the degradable polymer mixture in thediscontinuous phase by any suitable process including, but not limitedto, vacuum stripping, steam stripping, evaporation, and the like. Anysuitable shearing device may be used in these methods including, but notlimited to, high speed dispersers, jet nozzles, in-line mixers, and thelike.

In alternative embodiments, the emulsion methods of this inventioninvolve providing a degradable polymer solvent mixture; adding a secondsolvent to the degradable polymer solvent mixture with sufficient shearto form a first emulsion, the first emulsion comprising a discontinuousphase that comprises the second solvent and a continuous phase thatcomprises the degradable polymer solvent mixture; continuing to add thesecond solvent to the first emulsion until phase inversion occurs toform a second emulsion, the second emulsion comprising a discontinuousphase that comprises the degradable polymer solvent mixture and acontinuous phase that comprises the second solvent; remove the firstsolvent from the discontinuous phase of the second emulsion so thatdegradable particulates begin to form; and allowing a dispersion ofdegradable particulates to form in the continuous phase of the secondemulsion. The first solvent can be removed from the degradable polymermixture in the discontinuous phase by any suitable process including,but not limited to, vacuum stripping, steam stripping, evaporation, andthe like. Any suitable shearing device may be used in these methodsincluding, but not limited to, high speed dispersers, jet nozzles,in-line mixers, and the like.

The resultant degradable particulates can be used in a subterraneanapplication with or without a treatment fluid, depending on the use. Insome embodiments, the second solvent may be the treatment fluid. Thismay be beneficial when a high concentration of degradable particulatesin the fluid is desired. In alternative embodiments, the degradableparticulates can be made in a batch process at the drill site and thenat a desired time, they may be added to a process stream to be placed ina subterranean formation. This method may be useful when a lowerconcentration of degradable particulates is desired for the application.

The important aspect to keep in mind with respect to the emulsionmethods of the present invention is that the first solvent and thesecond solvent should be immiscible.

The degradable polymer solvent mixture may be any suitable type ofmixture of a degradable polymer and a solvent including, but not limitedto, a solution, a suspension, or an emulsion. In one embodiment, thedegradable polymer solvent mixture may be formed by forming a degradablemonomer solvent mixture (which may be an emulsion, a solution, or asuspension), and then reacting the degradable monomer solvent mixture topolymerize the monomer to form a degradable polymer solvent mixture thatmay be used to form degradable particulates. One of ordinary skill inthe art with the benefit of this disclosure will recognize the amount ofheat or a suitable catalyst will be needed to affect polymerization. Oneconsideration will be the type of monomer and solvent used. Any suitableheating device may be used.

Examples of suitable degradable polymers that may be used in conjunctionwith the emulsion methods of this invention include, but are not limitedto, aliphatic polyesters; poly(lactides); poly(glycolides);poly(ε-caprolactones); poly(hydroxy ester ethers);poly(hydroxybutyrates); poly(anhydrides); polycarbonates;poly(orthoesters); poly(amino acids); poly(ethylene oxides);poly(phosphazenes); poly ether esters, polyester amides, polyamides, andcopolymers or blends of any of these degradable polymers. The term“copolymer” as used herein is not limited to the combination of twopolymers, but includes any combination of polymers, e.g., terpolymersand the like. Of these suitable polymers, aliphatic polyesters such aspoly(lactic acid), poly(anhydrides), poly(orthoesters), andpoly(lactide)-co-poly(glycolide) copolymers are preferred. Poly(lacticacid) is especially preferred. Poly(orthoesters) also may be preferred.Other degradable polymers that are subject to hydrolytic degradationalso may be suitable. One's choice may depend on the particularapplication and the conditions involved. Other guidelines to considerinclude the degradation products that result, the time for required forthe requisite degree of degradation, and the desired result of thedegradation (e.g., voids). Others that are preferred include thosedegradable polymers that release useful or desirable degradationproducts that are desirable, e.g., an acid. Such degradation productsmay be useful in a downhole application, e.g., to break a viscosifiedtreatment fluid or an acid soluble component present therein (such as ina filter cake).

Preferred aliphatic polyesters have the general formula of repeatingunits shown below:

where n is an integer between 75 and 10,000 and R is a hydrogen, alkyl,aryl, alkylaryl, acetyl, heteroatoms, or mixtures thereof. Of thesealiphatic polyesters, poly(lactide) is preferred. Poly(lactide) issynthesized either from lactic acid by a condensation reaction or morecommonly by ring-opening polymerization of cyclic lactide monomer. Sinceboth lactic acid and lactide can achieve the same repeating unit, thegeneral term poly(lactic acid) as used herein refers to formula Iwithout any limitation as to how the polymer was made such as fromlactides, lactic acid, or oligomers, and without reference to the degreeof polymerization or level of plasticization. The lactide monomer existsgenerally in three different forms: two stereoisomers L- and D-lactideand racemic D,L-lactide (meso-lactide). The oligomers of lactic acid,and oligomers of lactide are defined by the formula:

where m is an integer 2≦m≦75. Preferably m is an integer and 2≦m≦10.These limits correspond to number average molecular weights below about5,400 and below about 720, respectively. The chirality of the lactideunits provides a means to adjust, inter alia, degradation rates, as wellas physical and mechanical properties. Poly(L-lactide), for instance, isa semicrystalline polymer with a relatively slow hydrolysis rate. Thiscould be desirable in applications of the present invention where aslower degradation of the degradable particulates is desired.Poly(D,L-lactide) may be a more amorphous polymer with a resultantfaster hydrolysis rate. This may be suitable for other applicationswhere a more rapid degradation may be appropriate. The stereoisomers oflactic acid may be used individually or combined to be used inaccordance with the present invention. Additionally, they may becopolymerized with, for example, glycolide or other monomers likeε-caprolactone, 1,5-dioxepan-2-one, trimethylene carbonate, or othersuitable monomers to obtain polymers with different properties ordegradation times. Additionally, the lactic acid stereoisomers can bemodified to be used in the present invention by, inter alia, blending,copolymerizing or otherwise mixing the stereoisomers, blending,copolymerizing or otherwise mixing high and low molecular weightpoly(lactides), or by blending, copolymerizing or otherwise mixing apoly(lactide) with another polyester or polyesters.

Plasticizers may be included in the degradable polymers of the presentinvention. The plasticizers may be present in an amount sufficient toprovide the desired characteristics, for example, a desired tackiness tothe generated degradable particulates. In addition to the otherqualities above, the plasticizers may enhance the degradation rate ofthe degradable polymeric materials. The plasticizers, if used, arepreferably at least intimately incorporated within the degradablepolymers. An example of a suitable plasticizer for poly(lactide) wouldinclude oligomeric lactic acid. Examples of plasticizers useful for thisinvention include, but are not limited to, polyethylene glycol;polyethylene oxide; oligomeric lactic acid; citrate esters (such astributyl citrate oligomers, triethyl citrate, acetyltributyl citrate,and acetyltriethyl citrate); glucose monoesters; partially fatty acidesters; PEG monolaurate; triacetin; poly(e-caprolactone);poly(hydroxybutyrate); glycerin-1-benzoate-2,3-dilaurate;glycerin-2-benzoate-1,3-dilaurate; bis(butyl diethylene glycol)adipate;ethylphthalylethyl glycolate; glycerin diacetate monocaprylate; diacetylmonoacyl glycerol; polypropylene glycol (and epoxy derivatives thereof);poly(propylene glycol)dibenzoate, dipropylene glycol dibenzoate;glycerol; ethyl phthalyl ethyl glycolate; poly(ethyleneadipate)distearate; di-iso-butyl adipate; and combinations thereof. Thechoice of an appropriate plasticizer will depend on the particulardegradable polymer utilized. It should be noted that, in certainembodiments, when initially formed, the degradable particulates may besomewhat pliable. But once substantially all of the solvent has beenremoved, the particulates should harden. More pliable degradableparticulates may be beneficial in certain chosen applications. Theaddition of presence of a plasticizer can affect the relative degree ofpliability. Also, the relative degree of crystallinity and amorphousnessof the degradable polymer can affect the relative hardness of thedegradable particulates.

In some of these emulsion method embodiments, to form an emulsion, anyemulsifying surfactant capable of forming an emulsion of a degradablepolymer solvent mixture and the second solvent may be included. Examplesof suitable emulsifying surfactants include any cationic, anionic, ornonionic surfactant capable of forming an emulsion as described herein.Specific examples include, but are not limited to, sodium dodecylsulfate, poly(vinyl alcohol), sodium dodecylbenzenesulfonic acid,cetyltrimethylammonium bromide, cetylpyridinium bromide,hexadecylmaltoside, Triton™ X-100, Tween 20, Brij W1, and Tergitol™NP-40. Polyvinyl alcohol is a preferred surfactant when water is used asa continuous phase solvent. Other emulsifying surfactants include freefatty acids, esters of fatty acids, with polyoxalkylene compounds (likepolyoxyethylene glycol, fatty acid esters with sorbitan, soaps, etc.).The choice of which particular emulsifying surfactant to use may bedetermined by the particular degradable polymer, first solvent, andsecond solvent used in any given embodiment. In certain embodiments, theemulsifying surfactant should be included in an amount sufficient tostabilize the emulsion. In some embodiments, this may be from about 0.1%to about 5% by weight of the continuous phase. The amount of emulsifyingsurfactant to include may depend on the identify of the degradablepolymer; the identities of the first solvent and second solvent; theparticular surfactant used and how well that surfactant stabilizes theemulsion; and the ability of the particular emulsifying surfactantchosen to potentially help prevent the agglomeration of degradableparticulates once formed.

The choice of first solvent for the degradable polymer solvent mixturein the emulsion methods of this invention will depend primarily on itsinteraction with the chosen second solvent. The first solvent and thesecond solvent in the emulsion methods should be immiscible, andtherefore, should be chosen vis-a-vis the other. Other guidelines usefulfor choosing a first solvent include, inter alia, the particulardegradable polymer chosen, the emulsifying surfactant used, theconcentration of the degradable polymer in the degradable polymersolvent mixture, and other similar factors. Examples include, but arenot limited to, acetone, chloroform, dichloromethane,1,2-dichlorobenzene, tetrahydrofuran, benzene, acetonitrile, dioxane,dimethylformamide, toluene, ethyl acetate, N-methylpyrrolidone, xylene,ether, diphenyl ether, ethylbenzene, naphthalene, propylene carbonate,di(propylene glycol) methyl ether, di(propylene glycol) propyl ether,di(propylene glycol) butyl ether, di(propylene glycol) methyl etheracetate, derivatives thereof, and combinations thereof. If thedegradable polymer used is poly(lactic acid), then a preferred solventmay be dichloromethane or chloroform, depending on the surroundingcircumstances. Other considerations to be taken into account whenchoosing a first solvent include safety and industrial hygiene, anypotential environmental issues, potential safety issues in terms offlash point and potential exposure, and relative cost. The first solventshould be included in an amount sufficient so that the degradablepolymer solvent mixture has a low enough viscosity such that when it isadded to the second solvent with shear, the degradable polymer solventmixture forms a discontinuous phase in the second solvent. This amountwill vary based on several characteristics including, the particulardegradable polymer utilized, the molecular weight of the degradablepolymer, the concentration of the degradable polymer in the degradablepolymer solvent mixture, and the like. One of ordinary skill in the artwith the benefit of this disclosure will be able to recognize theappropriate amount to include taking into account these considerations.Preferably, a minimal amount of the first solvent should be used wherepossible because that solvent will be removed to form degradableparticulates. In preferred embodiments, the first solvent should besubstantially removed from the degradable polymer emulsion discontinuousphase to allow degradable particulates to form in a more beneficialmanner. In certain embodiments, the amount of first solvent includedwill range from about 5% to about 80% based on the amount of thedegradable polymer that is included in the degradable polymer solventmixture. In one example of one embodiment wherein poly(lactic acid) isused, dichloromethane may be used in an amount of 50% to 80% based onthe weight of poly(lactic acid) used.

Second solvents should be chosen relative to the first solvent such thatthe first solvent and second solvent are immiscible. Suitable examplesof second solvents that may be used in the emulsion methods of thisinvention include any fluid in which the degradable polymer isrelatively insoluble and that is capable of interacting with the firstsolvent in such a way as to allow ultimately at least partially removalof the first solvent from the degradable polymer emulsion discontinuousphase so that degradable particulates may form in the second solvent.Preferred second solvents are aqueous-based. Suitable aqueous-basedfluids may comprise a water source such as fresh water, saltwater (e.g.,water containing one or more salts dissolved therein), brine (e.g.,saturated saltwater), or seawater. Generally, the water source can befrom any source, provided that it does not contain an excess ofcompounds that may adversely affect the degradable polymer emulsionand/or the formation of degradable particulates. Potentially problematiccompounds to be mindful of will be evident to one skilled in the artwith the benefit of this disclosure. Examples of nonaqueous secondsolvents that may be used include ethanol, isopropanol, and polyhydricalcohols such as glycerol. As stated above, the second solvent may be atreatment fluid that will be introduced into the subterranean formation(e.g., a fracturing fluid, a gravel pack fluid, a drilling fluid, etc.).Thus, in such embodiments, the resultant degradable particulates may beintroduced into the subterranean formation with the second solvent,which would be the treatment fluid used in that particular application.The second solvent should be included in an embodiment of the emulsionmethods of this invention in an amount sufficient to aid in the removalof the first solvent from the degradable polymer so that degradableparticulates form and in at least an amount sufficient to form anadequate emulsion. The amount of second solvent to use may varydepending on certain factors, for example, the desired characteristicsof the resultant degradable particulates; the concentration of thedegradable polymer solvent mixture in the second solvent; theconcentration of the degradable polymer in the degradable polymersolvent mixture, and the amount of degradable particulates to beproduced. In some embodiments, the amount of second solvent to includemay be less than about 1% to more than about 95% relative to theemulsion. To ensure that desirable degradable particulates form, thedegradable polymer should not be soluble in the second solvent. Ifdesired, optionally additives such as oxidizers, salts, or otherchemical agents may be included such that when the degradableparticulates form, the additives become incorporated within theparticulates. Any additive that is capable of becoming incorporated intothe degradable particulates during the emulsion process may be used. Anysuch additives may have a specific desirable functionality. For example,some additives may modulate the rate of hydrolysis of the degradableparticulates depending on the conditions encountered in the particularapplication. Including an additive may be desirable when it would bebeneficial to introduce the additive into the subterranean formationupon or during degradation of the degradable particulates. Whencontemplating the addition of an additive, one should be mindful thatthe additive should not adversely affect other operations or components.In an example of an alternative embodiment, an acid-soluble solidmaterial may be added to the degradable polymer emulsion so that theacid-soluble material becomes incorporated into the resultant degradableparticulates. Examples of suitable acid-soluble solid materials include,but are not limited to, calcium carbonate and magnesium oxide. This maybe desirable, for example, to neutralize the acid generated upondegradation of the degradable particulates, to modulate the hydrolysisof the degradable particulates, or to add crush strength to thedegradable particulates.

In these embodiments, the average size distribution of the resultantdegradable particulates may vary, depending on several factors. Thesefactors include, but are not limited to, the type of emulsifyingsurfactant used, the amount of emulsifying surfactant used, the type offirst solvent used, the type of second solvent used, the chemicalinteraction between the first solvent and the second solvent, theparticular degradable polymer used, the molecular weight of thedegradable polymer, the concentration of the degradable polymer in thedegradable polymer solvent mixture; the amount of shear applied; thepresence of certain additives, the temperature conditions, etc. Thedesired average particulate size distribution can be modified as desiredby modifying any of these factors. One of ordinary skill in the art withthe benefit of this disclosure will be able to identify the particularfactor to modify to achieve a desired particulate size distribution.

The Precipitation Methods of This Invention

The present invention provides precipitation methods that may be used togenerate degradable particulates of a suitable or desirable size andshape at a drill site for use in subterranean applications. Thedegradable particulates can be used in a subterranean application withor without a treatment fluid, depending on the use.

A method for forming degradable particulates at a drill site comprises:providing a degradable polymer solvent mixture that comprises adegradable polymer and a first solvent; and mixing the degradablepolymer solvent mixture in a second solvent with shear to form a solidliquid dispersion comprising a solid phase and a liquid phase, the solidphase comprising degradable particulates and the liquid phase comprisingthe first solvent and the second solvent. In these precipitationmethods, the first solvent and the second solvent should be soluble ineach other. Most preferably, the first solvent should be more soluble inthe second solvent than the degradable polymer. As a result of, interalia, this solubility the first solvent should go from the degradablepolymer solvent mixture to the second solvent without an additionalremoval step.

Any suitable shearing device may be used in these methods including, butnot limited to, high speed dispersers, jet nozzles, in-line mixers, andthe like. The shearing device chosen should generate sufficient shear sothat the solid-liquid dispersion forms. One should note that theparticle size distribution of the resultant degradable particulates maybe a function of the shearing device and the amount of shear used. Forinstance, more or stronger shear may result in smaller particulates,depending on the degradable polymer utilized.

The resultant degradable particulates can be used in a subterraneanapplication with or without a treatment fluid, depending on the use. Insome embodiments, the second solvent may be the treatment fluid. Thismay be beneficial when a high concentration of degradable particulatesin the fluid is desired. In alternative embodiments, the degradableparticulates can be made in a batch process at the drill site and thenat a desired time, they may be added to a process stream to be placed ina subterranean formation. A batch method may be useful when a lowerconcentration of degradable particulates is desired for the application.

The important aspect to keep in mind with respect to the precipitationmethods of the present invention is that the first solvent should besoluble in the second solvent, and the degradable polymer used shouldnot be soluble in the second solvent.

The degradable polymer solvent mixture may be any suitable type ofmixture of a degradable polymer and a solvent including, but not limitedto, a solution, a suspension, or an emulsion. In one embodiment, thedegradable polymer solvent mixture may be formed by forming a degradablemonomer solvent mixture (which may be an emulsion, a solution, or asuspension), and then reacting the degradable monomer solvent mixture topolymerize the monomer to form a degradable polymer solvent mixture thatmay be used to form degradable particulates. One of ordinary skill inthe art with the benefit of this disclosure will recognize the amount ofheat, catalyst, or time will be needed to affect polymerization. Oneconsideration will be the type of monomer and solvent used. Any suitableheating device may be used.

In some embodiments, it may be desirable to add a surfactant at somepoint in the precipitation process, e.g., in the solid-liquiddispersion. Adding a surfactant may help prevent agglomeration of theresultant degradable particulates. In some embodiments, theprecipitation methods may be relatively slower than the emulsionmethods, which may result in the degradable particulates being moretacky and liable to agglomerate. If more pliable or tacky particulatesare desired for a given application, then a precipitation method of thisinvention may be most suitable. Examples of suitable emulsifyingsurfactants include any cationic, anionic, or nonionic surfactantcapable of preventing agglomeration of the particulates. Specificexamples include, but are not limited to, sodium dodecyl sulfate,poly(vinyl alcohol), sodium dodecylbenzenesulfonic acid,cetyltrimethylammonium bromide, cetylpyridinium bromide,hexadecylmaltoside, Triton™ X-100, Tween 20, Brij W1, and Tergitol™NP-40. The choice of which particular surfactant to use may bedetermined by the particular degradable polymer, first solvent, andsecond solvent used in any given embodiment. In certain embodiments, thesurfactant should be included in an amount sufficient to preventdegradable particulate agglomeration. In some embodiments, this may befrom about 0.1% to about 5% based on the amount of the second solvent.

The same degradable polymers are suitable for these methods as thoselisted and discussed above with respect to the emulsion methods of thepresent invention. Examples of suitable degradable polymers that may beused in conjunction with these methods include, but are not limited to,aliphatic polyesters; poly(lactides); poly(hydroxy ester ethers);poly(glycolides); poly(ε-caprolactones); poly(hydroxybutyrates);poly(anhydrides); polycarbonates; poly(orthoesters); poly(amino acids);poly(ethylene oxides); poly(phosphazenes); poly ether esters; polyesteramides; polyamides; and copolymers or blends of any of these degradablepolymers. Other degradable polymers that are subject to hydrolyticdegradation also may be suitable.

Plasticizers as discussed above with respect to the emulsion methods ofthis invention may be included in the degradable polymers, if desired.One should note though to achieve the most beneficial effects of thisinvention, it is preferred that the plasticizers should not be solublein the second solvent.

Additionally, the same suitable first solvents as those described abovewith respect to the emulsion methods of the present invention aresuitable for use in the precipitation methods of this invention. Inthese precipitation methods, one should remember that the first solventshould be chosen relative to the second solvent such that the firstsolvent is soluble in the second solvent. It also is preferred that thefirst solvent be capable of at least partially dissolving the degradablepolymer chosen. The choice of the first solvent should depend on thedegradable polymer used in a particular embodiment and the secondsolvent chosen. The first solvent should be included in an amountsufficient to form a degradable polymer solvent mixture that can bemixed with a second solvent to form a solid-liquid dispersion. Incertain embodiments, the amount of first solvent included will rangefrom about 5% to about 80% based on the amount of the degradable polymerthat is included in the degradable polymer solvent mixture. In oneexample of one embodiment wherein poly(lactic acid) is used, a propylenecarbonate first solvent may be used in an amount of 50% to 80% based onthe weight of poly(lactic acid) used.

The second solvent should be chosen in the precipitation methodsrelative to the first solvent such that the first solvent is soluble inthe second solvent. Preferred second solvents are aqueous-based.Suitable aqueous-based second solvents may comprise a water source suchas fresh water, saltwater (e.g., water containing one or more saltsdissolved therein), brine (e.g., saturated saltwater), or seawater.Generally, the water source can be from any source, provided that itdoes not contain an excess of compounds that may adversely affect theprocess or the formation of degradable particulates. Potentiallyproblematic compounds to be mindful of will be evident to one skilled inthe art with the benefit of this disclosure. Examples of nonaqueoussecond solvents that may be used include ethanol, isopropanol, or apolyhydric alcohol (such as glycerol or water soluble solvents). Asstated above, the second solvent may be a treatment fluid that will beintroduced into the subterranean formation (e.g., a fracturing fluid, agravel pack fluid, a drilling fluid, etc.). Thus, in such embodiments,the resultant degradable particulates may be introduced into thesubterranean formation with the second solvent, which would be thetreatment fluid used in that particular subterranean application. Thesecond solvent should be included in an embodiment of the precipitationmethods of this invention in an amount sufficient to form thesolid-liquid dispersion and allow the degradable particulates to form.The amount of second solvent to use may vary depending on certainfactors, for example, the identity of the first solvent; the quantity ofthe degradable polymer solvent mixture; the desired characteristics ofthe resultant degradable particulates; the concentration of thedegradable polymer solvent mixture in the second solvent; theconcentration of the degradable polymer in the degradable polymersolvent mixture, and the amount of degradable particulates to beproduced. In some embodiments, the amount of second solvent to includemay be less than about 1% to more than about 95% relative to themixture. To ensure that desirable degradable particulates form, thedegradable polymer should not be soluble in the second solvent.

If desired, optionally additives such as oxidizers, salts, or otherchemical agents may be included in the degradable polymer solventmixture such that when the degradable particulates form, the additivesare incorporated within the particulates. Any additive that is capableof becoming incorporated into the degradable particulates during theprecipitation process may be used. Preferably the additive should not besoluble in the first solvent, the second solvent, or the liquid phase ofthe solid-liquid dispersion. Any such additives may have a specificdesirable functionality. For example, some additives may modulate therate of hydrolysis of the degradable particulates depending on theconditions encountered in the particular application. Including anadditive may be desirable when it would be beneficial to introduce theadditive into the subterranean formation upon or during degradation ofthe degradable particulates. When contemplating the addition of anadditive, one should be mindful that the additive should not adverselyaffect other operations or components. In an example of an alternativeembodiment, an acid-soluble solid material may be added to thedegradable polymer solvent mixture so that the acid-soluble materialbecomes incorporated into the resultant degradable particulates.Examples of suitable acid-soluble solid materials include, but are notlimited to, calcium carbonate and magnesium oxide. This may bedesirable, for example, to neutralize the acid generated upondegradation of the degradable particulates, to modulate the hydrolysisof the degradable particulates, or to add crush strength to thedegradable particulates.

In these embodiments, the average size distribution of the resultantdegradable particulates may vary, depending on several factors. Thesefactors include, the type of first solvent used, the type of secondsolvent used, the chemical interaction between the first solvent and thesecond solvent, the particular degradable polymer used, the molecularweight of the degradable polymer, the concentration of the degradablepolymer in the degradable polymer solvent mixture; the amount of shearapplied; the type of shearing device, the presence of various additives,the temperature conditions, etc.

The Melt Coagulation Methods of this Invention

The melt coagulation methods of the present invention may be used toproduce degradable particulates of a suitable or desirable size andshape at the drill site for use in subterranean applications. Thedegradable particulates can be used in a subterranean application withor without a treatment fluid, depending on the use.

A melt coagulation method of this invention comprises the steps ofproviding a degradable polymer melt; atomizing the degradable polymermelt into an atomization fluid stream; and allowing degradableparticulates to form.

The degradable polymer melt may be formed by heating a degradablepolymer to at or above its melting point. The degradable polymer meltmay be formed at the drill site or brought to the drill site (e.g., in aheated tanker truck). Any suitable device to produce or provide adegradable polymer melt at the drill site may be used in the meltcoagulation methods of this invention. Shear may be incorporated intosuch a device, if desired.

During the atomization step, the degradable polymer melt is atomizedinto a atomization fluid stream in which the degradable polymer is notsoluble. The atomization fluid stream may comprise a gas or a liquid,depending on the particular application. Pressure may be desirable toencourage the melt to proceed through the atomization device. Anysuitable atomization device may be used in the melt coagulation methodsof the present invention. One example of a suitable atomization deviceis a nozzle that has an appropriate diameter to produce degradableparticulates having a desired shape or size. In some embodiments, thesame sort of equipment used in applications to spray hot melt adhesivesmay be used. The degradable polymer melt may be atomized into anatomization fluid stream, which may comprise a liquid and/or a gas. Theatomization fluid stream may comprise a treatment fluid in which thedegradable particulates will be introduced into a subterranean formationfor a desired application. In choosing the appropriate atomization fluidstream, one should be mindful that the degradable particulates shouldnot be soluble in the atomization fluid stream. The desiredconcentration of degradable particulates in a treatment fluid may governwhat type of fluid is used in the atomization fluid stream, includingwhether atomizing into a treatment fluid is appropriate. During thisstep, one should be mindful that the atomization should be done in sucha manner that whole droplets of a desired size and shape are formed sothat the resultant degradable particulates will have the desired shapeand size. Atomization may occur in any suitable apparatus. A fluidizedbed reactor is an example of a suitable apparatus. A high pressurenozzle is another example of a suitable apparatus. Preferred apparatushave a sufficient amount of fluid and the temperature is low enough toallow the degradable particulates to cool and form degradableparticulates. The temperature and pressure at which the atomization isaccomplished may impact greatly the size and shape of the resultantdegradable particulates. Other factors that can affect the qualities ofthe resultant degradable particulates include the particular atomizationdevice, the orifice of the atomization device, the temperature of themelt, the temperature and pressure conditions of the atomizationprocess, etc.

If desired, optionally, the degradable polymer melt may compriseadditional additives as long as they are not sensitive to or negativelyimpacted by the heating of the melt. Any such additives also should notnegatively impact the degradable polymer melt itself, the atomizationprocess or the formation of degradable particulates. Examples ofsuitable additives include oxidizers, salts, or other chemical agentsthat are desirable to have incorporated in the resultant degradableparticulates. Any additive that is capable of becoming incorporated intothe degradable particulates during a melt coagulation process may beused. Any such additives may have a specific desirable functionality.For example, some additives may modulate the rate of hydrolysis of thedegradable particulates depending on the conditions encountered in theparticular application. Including an additive may be desirable when itwould be beneficial to introduce the additive into the subterraneanformation upon or during degradation of the degradable particulates.When contemplating the addition of an additive, one should be mindfulthat the additive should not adversely affect other operations orcomponents. In an example of an alternative embodiment, an acid-solublesolid material may be added to the degradable polymer melt so that theacid-soluble material becomes incorporated into the resultant degradableparticulates. Examples of suitable acid-soluble solid materials include,but are not limited to, calcium carbonate and magnesium oxide. This maybe desirable, for example, to neutralize the acid generated upondegradation of the degradable particulates, to modulate the hydrolysisof the degradable particulates, or to add crush strength to thedegradable particulates.

Although all of the degradable polymers discussed above with respect tothe emulsion and precipitation methods may be used in the meltcoagulation methods of this invention, the particular degradable polymerchosen for a melt coagulation method preferably has a relatively lowermolecular weight and melt viscosity. Also, degradable polymers that willform droplets upon atomization are preferred. Examples of suitabledegradable polymers that may be used in conjunction with the emulsionmethods of this invention include, but are not limited to, aliphaticpolyesters; poly(lactides); poly(hydroxy ester ethers);poly(glycolides); poly(ε-caprolactones); poly(hydroxybutyrates);poly(anhydrides); polycarbonates; poly(orthoesters); poly(amino acids);poly(ethylene oxides); poly(phosphazenes); poly ether esters; polyesteramides; polyamides; and copolymers or blends of any of these degradablepolymers. Preferred examples of degradable polymers for use in the meltcoagulation methods of this invention include poly(lactides),poly(glycolides), poly(ε-caprolactones), and poly(hydroxybutyrates).Other degradable polymers that are subject to hydrolytic degradationalso may be suitable.

Plasticizers may be included in the degradable polymers to achievedesired properties in the resultant degradable particulates or thedegradable polymer melt. Any of the above listed plasticizers aresuitable for use in the melt coagulation methods of this invention aslong as they are tolerant to the melt and atomization processes suchthat the plasticizer remains in the resultant degradable particulates toprovide desired properties. The choice of plasticizer(s) will depend onthe particular degradable polymer chosen for a particular embodiment ofthese melt coagulation methods and the application in which thedegradable particulates will be used. In some embodiments, plasticizersmay be particularly helpful to increase the melt viscosity and improveatomization of the melt.

One should note that if the resultant degradable particulates will beused in conjunction with a nonaqueous treatment fluid, the meltcoagulation methods of this invention may be preferred as long as thenonaqueous fluid does not dissolve the degradable particulates.

In certain embodiments, it may be desirable to include a surfactant inthe atomization fluid. The surfactant may help disperse the degradableparticulates in the atomization fluid. Examples of suitable surfactantsinclude any cationic, anionic, or nonionic surfactant capable of helpingdisperse the degradable particulates in the atomization fluid. Specificexamples include, but are not limited to, sodium dodecyl sulfate,poly(vinyl alcohol), sodium dodecylbenzenesulfonic acid,cetyltrimethylammonium bromide, cetylpyridinium bromide,hexadecylmaltoside, Triton™X-100, Tween 20, Brij W1, and Tergitol™NP-40.The choice of which particular surfactant to use may be determined bythe particular degradable polymer chosen, the melt conditions, and theatomization process chosen. In certain embodiments, the surfactantshould be included in an amount sufficient to prevent degradableparticulate agglomeration. In some embodiments, this may be from about0.1% to about 5% based on the amount of degradable particulates in theatomization fluid.

The particle size of the degradable particulates can be altered bychanging various factors in the process. For instance, the melttemperature, the particular atomization device, the conditionsencountered in the atomization device (e.g., temperature and pressure),the rate at which the atomization occurs, additives, and the like mayall be altered to produce degradable particulates having differing sizesand/or characteristics. One of ordinary skill in the art with thebenefit of this disclosure will recognize the variables and the degreeof variation required to produce the degradable particulates for use ina particular application.

The Supercritical Fluid Assisted Methods of this Invention

The supercritical fluid assisted methods of the present invention may beused to produce degradable particulates of a suitable or desirable sizeand shape at the drill site for use in subterranean applications. Thedegradable particulates can be used in a subterranean application withor without a treatment fluid, depending on the use. These supercriticalfluid assisted methods may be especially useful for forming smallerdegradable particulates. For instance, in certain embodiments, thesemethods may be used to produce 1 to 3 μm degradable particulates thatmay have a lower tendency to agglomerate.

Although other supercritical fluids may be suitable, supercriticalcarbon dioxide is a preferred supercritical fluid in these methods.Generally speaking, the use of a supercritical carbon dioxide isdesirable because it is considered an environmentally friendly solventsubstitute. Carbon dioxide is considered to be nontoxic, nonflammable,and has easily accessible critical conditions, i.e., T_(c)=31 ° C. andP_(c)=7.37 MPa.

An example of a supercritical fluid assisted method of this invention isa method of forming degradable particulates at a drill site thatcomprises: providing a degradable polymer supercritical fluid mixture;allowing the degradable polymer supercritical fluid mixture to expandthrough an orifice into a lower pressure zone; and allowing degradableparticulates to form. The lower pressure zone may be any suitable lowerpressure area including, but not limited to, a chamber in a piece ofequipment, a fluid, a treatment fluid in which the resultant degradableparticulates will be introduced into a subterranean formation, or thelike. The degradable polymer supercritical fluid mixture may be mixed atthe drill site or premixed at a second location and then brought to thedrill site.

In alternative embodiments, a suitable solvent and/or a surfactant maybe incorporated into the degradable polymer supercritical fluid mixture,for example, when the degradable polymer is not sufficiently soluble inthe supercritical fluid without the solvent or surfactant. Any solventor surfactant that will aid in the dissolution of the degradable polymerin the supercritical carbon dioxide is suitable. Preferred solvents andsurfactants also are compatible with the circumstances surrounding theparticular subterranean application of the degradable particulates. Theparticular solvent or surfactant used depends in large part on theidentity of the degradable polymer chosen for a specific embodiment.

The choice of an optional solvent for the degradable polymersupercritical fluid mixture in the emulsion methods of this inventionwill depend, inter alia, on the particular degradable polymer chosen,the concentration of the degradable polymer in the supercriticaldegradable polymer mixture, etc. Examples of suitable solvents include,but are not limited to, acetone, chloroform, dichloromethane,1,2-dichlorobenzene, tetrahydrofuran, benzene, acetonitrile, dioxane,dimethylformnamide, toluene, ethyl acetate, N-methylpyrrolidone, xylene,ether, diphenyl ether, ethylbenzene, naphthalene, propylene carbonate,di(propylene glycol) methyl ether, di(propylene glycol) propyl ether,di(propylene glycol) butyl ether, di(propylene glycol) methyl etheracetate, derivatives thereof, and combinations thereof. Fluorinatedalcohols and fluorinated hydrocarbons may be especially useful,depending on the particular degradable material chosen and theconditions of the particular application. In choosing a solvent to usein an embodiment of a supercritical fluid assisted method of thisinvention, one should be mindful of the properties of that solvent andany regulations that may apply, especially if the degradableparticulates will be made on-the-fly, which could result in at leastsome of the solvent being introduced into a subterranean formation.Other considerations to be taken into account when choosing a solventinclude safety and industrial hygiene, any potential environmentalissues, potential safety issues in terms of flash point and potentialexposure, and relative cost. If used, the solvent should be included inan amount sufficient to aid in the formation of the degradable polymersupercritical fluid mixture.

Examples of suitable optional surfactants that may be used in thesemethods include any cationic, anionic, or nonionic surfactant. Specificexamples include, but are not limited to, sodium dodecyl sulfate,poly(vinyl alcohol), sodium dodecylbenzenesulfonic acid,cetyltrimethylammonium bromide, cetylpyridinium bromide,hexadecylmaltoside, Triton™ X-100, Tween 20, Brij W1, and Tergitol™NP-40. The choice of which particular surfactant to use may bedetermined by the particular degradable polymer chosen. In certainembodiments, the surfactant should be included in an amount sufficientto stabilize the degradable polymer supercritical fluid mixture. In someembodiments, this may be from about 0.1% to about 5% based on the amountof degradable polymer in a degradable polymer supercritical fluidmixture.

All of the degradable polymers discussed above with respect to theemulsion, precipitation, and melt coagulation methods may be used in thesupercritical fluid assisted methods of this invention. Examplesinclude, but are not limited to, aliphatic polyesters; poly(lactides);poly(glycolides); poly(hydroxy ester ethers); poly(ε-caprolactones);poly(hydroxybutyrates); poly(anhydrides); polycarbonates;poly(orthoesters); poly(amino acids); poly(ethylene oxides);poly(phosphazenes); polyether esters; polyester amides; polyamides;copolymers or blends of any of these degradable polymers. Plasticizersmay be included in the degradable polymers to achieve the desiredproperties. Any plasticizer is suitable as long as it is not negativelyimpacted by or does not negatively impact the formation of thedegradable particulates. In choosing the particular degradable polymerfor a chosen application, one should note that some of the degradablepolymers may have lower solubility in supercritical carbon dioxide thanothers. This relative solubility should be taken into account whenmixing or providing a degradable polymer supercritical fluid mixture. Asstated above, solvents or surfactants may be included if needed.

Allowing the degradable polymer supercritical fluid mixture to expandthrough an orifice into a lower pressure zone may be accomplished by anysuitable method. The degradable polymer supercritical fluid mixture maybe allowed to expand through a suitable nozzle, for example, into a zonehaving a lower pressure. One should note that the pressure andtemperature conditions used in the expansion step may affect the sizeand properties of the resultant degradable particulates. The geometry ofthe orifice also can greatly affect the characteristics of the resultantdegradable particulates. The concentration of the degradable polymer inthe degradable polymer supercritical fluid mixture also may affect theproperties of the resultant degradable particulates. The lower pressurezone may be internal to or external to a well bore in subterraneanformation. In some embodiments, the lower pressure zone may comprise atreatment fluid in which the degradable particulates will be introducedinto a subterranean formation.

Examples of Suitable Subterranean Applications

The degradable particulates can be used in a subterranean applicationwith or without a treatment fluid, depending on the particularapplication and the surrounding circumstances. One of ordinary skill inthe art with the benefit of this disclosure will be able to recognizewhen the degradable particulates should be or should not be used inconjunction with a treatment fluid. One consideration is the ability toincorporate the degradable particulates in the treatment fluid. Anotherconsideration is the timing desired for the degradation of thedegradable particulates. Another consideration is the concentration ofdegradable particulates needed in a chosen treatment fluid.

The degradable particulates made by any method of this invention may beused in any suitable subterranean application. Depending on theparticular use, the degradable particulates may have several purposes.The first is to create voids upon degradation. A second is to releasecertain desirable degradation products that may then be useful for aparticular function. Another reason is to temporarily restrict the flowof a fluid. Examples of subterranean applications in which the generateddegradable particulates could be used include, but are not limited to,such applications as fluid loss control particles, as diverting agents,as filter cake components, as drilling fluid additives, as cementcomposition additives, or other acid-precursor components. Specificnonlimiting embodiments of some examples are discussed below.

In some methods, the degradable particulates may be used to increase theconductivity of a fracture. This may be accomplished by incorporatingthe degradable particulates into a fracturing fluid comprising proppantparticulates, allowing the proppant particulates to form a proppantmatrix within a fracture that comprises the degradable particulates, andallowing the degradable particulates to degrade to form voids within theproppant matrix. The term “proppant matrix” refers to some consolidationof proppant particulates.

In another example of a subterranean application, the degradableparticulates may be used to divert a fluid within a subterraneanformation.

In another example, the degradable particulates may be used in acomposition designed to provide some degree of sand control to a portionof a subterranean formation. In an example of such a method, thedegradable particulates may be incorporated into a cement compositionwhich is placed down hole in a manner so as to provide some degree ofsand control. An example of such a cement composition comprises ahydraulic cement, sufficient water to form a pumpable slurry, and thedegradable particulates formed by a method of this invention.Optionally, other additives used in cementing compositions may be added.

In another example, the degradable particulates may be incorporated intoa cement composition to be used in a primary cementing operation, suchas cementing casing in a well bore penetrating a subterranean formation.An example of such a cement composition comprises a hydraulic cement,sufficient water to form a pumpable slurry, and the degradableparticulates formed by a method of this invention. Optionally, otheradditives used in cementing compositions may be added.

In another example, the degradable particulates may be incorporated in agravel pack composition. Upon degradation of the degradableparticulates, any acid-based degradation products may be used to degradean acid-soluble component in the subterranean formation, including butnot limited to a portion of a filter cake situated therein.

In another example, the degradable particulates may be incorporated witha viscosified treatment fluid (e.g., a fracturing fluid or a gravel packfluid) to act as a breaker for the viscosified treatment fluid (i.e., atleast partially reduce the viscosity of the viscosified treatmentfluid).

In another example, the degradable particulates may be used asself-degrading bridging agents in a filter cake.

In another example, the degradable particulates may be used as a fluidloss control additive for at least partially controlling or minimizingfluid loss during a subterranean treatment such as fracturing.

In another example, the degradable particulates may be used inconjunction with cleaning or cutting a surface in a subterraneanformation.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Whilenumerous changes may be made by those skilled in the art, such changesare encompassed within the spirit of this invention as defined by theappended claims.

1. A method comprising: providing a degradable polymer solvent mixturethat comprises a degradable polymer and a first solvent; and mixing thedegradable polymer solvent mixture with a second solvent at a drill sitewith shear to form a solid liquid dispersion comprising a solid phaseand a liquid phase, the solid phase comprising degradable particulatesand the liquid phase comprising the first solvent and the secondsolvent.
 2. The method of claim 1 wherein the first solvent and thesecond solvent are at least partially soluble in each other.
 3. Themethod of claim 1 wherein the shear is introduced by a high speeddisperser, a jet nozzle, or an in-line mixer.
 4. The method of claim 1wherein the second solvent comprises a treatment fluid in which thedegradable particulates will be introduced into a subterraneanformation.
 5. The method of claim 1 wherein the degradable polymersolvent mixture is a solution, suspension, or an emulsion.
 6. The methodof claim 1 wherein the solid liquid dispersion comprises a surfactant.7. The method of claim 1 wherein the degradable polymer comprises atleast one of the following: an aliphatic polyester; a poly(lactide); apoly(hydroxy ester ether); a poly(glycolide); a poly(ε-caprolactone); apoly(hydroxybutyrate); a poly(anhydride); an aliphatic polycarbonate; apoly(orthoester); a poly(amino acid); a poly(ethylene oxide); apoly(phosphazene); a polyether ester; a polyester amide; a polyamide; acopolymer or a blend thereof.
 8. The method of claim 1 wherein thedegradable polymer comprises a plasticizer.
 9. The method of claim 1wherein the second solvent comprises an aqueous-based solvent and thefirst solvent is soluble in the second solvent.
 10. The method of claim1 wherein in the degradable polymer solvent mixture comprises anoxidizer, a salt, or an acid-soluble material.
 11. The method of claim 1further comprising using at least a portion of the degradableparticulates in a subterranean application to divert a fluid within thesubterranean formation.
 12. The method of claim 1 further comprisingincorporating at least a portion of the degradable particulates into aviscosified treatment fluid, the degradable particulates being capableof acting as a viscosity breaker for the viscosified treatment fluid.13. The method of claim 1 further comprising incorporating at least aportion of the degradable particulates into a gravel pack.
 14. Themethod of claim 1 further comprising incorporating at least a portion ofthe degradable particulates into a filter cake, at least a portion ofthe degradable particulates being capable of acting as degradablebridging agents in the filter cake.
 15. The method of claim 1 furthercomprising placing at least a portion of the degradable particulates ina cement composition that comprises a hydraulic cement and water. 16.The method of claim 1 further comprising using at least a portion of thedegradable particulates as fluid loss control agents in a subterraneanapplication.
 17. The method of claim 1 further comprising: incorporatingat least a portion of the degradable particulates into a fracturingfluid that comprises proppant particulates; allowing a portion of theproppant particulates to form a proppant matrix that comprises at leasta plurality of the degradable particulates within a fracture in asubterranean formation; and allowing the degradable particulates todegrade so as to form at least one void in the proppant matrix.
 18. Amethod comprising: providing a treatment fluid at a drill site, thetreatment fluid comprising degradable particulates, wherein at least aportion of the degradable particulates have been made by a precipationmethod at the drill site; and introducing the treatment fluid into awell bore penetrating a subterranean formation at the drill site. 19.The method of claim 18 wherein the degradable polymer comprises at leastone of the following: an aliphatic polyester; a poly(lactide); apoly(hydroxy ester ether); a poly(glycolide); a poly(ε-caprolactone); apoly(hydroxybutyrate); a poly(anhydride); an aliphatic polycarbonate; apoly(orthoester); a poly(amino acid); a poly(ethylene oxide); apoly(phosphazene); a polyether ester; a polyester amide; a polyamide; acopolymer or a blend thereof.
 20. A method comprising: providing adegradable polymer solvent mixture that comprises a degradable polymerand a first solvent; mixing the degradable polymer solvent mixture witha second solvent at a drill site with shear to form a solid liquiddispersion comprising a solid phase and a liquid phase, the solid phasecomprising degradable particulates and the liquid phase comprising thefirst solvent and the second solvent; and introducing the second solventand at least a portion of the degradable particulates into a well borepenetrating a subterranean formation at the drill site.